Light availability in the coastal ocean: impact on the distribution of benthic photosynthetic organisms and contribution to primary production

• Main Authors: Gattuso, Jean-Pierre, Gentili, B., Duarte, C. M., Kleypas, J. A., Middelburg, J. J., Antoine, D.
• Other Authors: Observatoire océanologique de Villefranche-sur-mer (OOVM), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Instituto Mediterraneo de Estudios Avanzados, CSIC-UIB, National Center for Atmospheric Research Boulder (NCAR), Netherlands Institute of Ecology (NIOO-KNAW)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2006
• Subjects: [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO]; [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph]; [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces; environment; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; Arctic
• Online Access: https://hal.science/hal-00330224; https://hal.science/hal-00330224/document; https://hal.science/hal-00330224/file/bgd-3-895-2006.pdf

International audience One of the major features of the coastal zone is that part of its sea floor receives a significant amount of sunlight and can therefore sustain benthic primary production by seagrasses, macroalgae, microphytobenthos and corals. However, the contribution of benthic communities to the primary production of the global coastal ocean is not known, partly because the surface area where benthic primary production can proceed is poorly quantified. Here, we use a new analysis of satellite (SeaWiFS) data collected between 1998 and 2003 to estimate, for the first time at a nearly global scale, the irradiance reaching the bottom of the coastal ocean. The following cumulative functions provide the percentage of the surface of the coastal zone receiving an irradiance greater than E z : P a Non-polar =28.80-16.69 log 10 ( E z )+0.84 log 10 2 ( E z )+0.83 log 10 3 ( E z ) P a Arctic =16.01-15.67 log 10 ( E z )+2.03 log 10 2 ( E z )+1.00 log 10 3 ( E z ) Data on the constraint of light availability on the major benthic primary producers and net primary production are reviewed. Some photosynthetic organisms can grow deeper than the nominal bottom limit of the coastal ocean (200 m). The minimum irradiance required varies from 0.4 to 5.1 mol photons m -2 d -1 depending on the group considered. The daily compensation irradiance of benthic communities ranges from 0.24 to 4.4 mol photons m -2 d -1 . Data on benthic irradiance and light requirements are combined to estimate the surface area of the coastal ocean where (1) light does not limit the distribution of primary producers and (2) net community production (NCP, the balance between gross primary production and respiration) is positive. Positive benthic NCP can occur over 37% of the global shelf area. The limitations of this approach, related to the spatial resolution of the satellite data, the parameterization used to convert reflectance data to irradiance, and the relatively limited biological information available, are discussed.